diff --git a/README.md b/README.md
index 3c107f0b8..54e0165b9 100644
--- a/README.md
+++ b/README.md
@@ -53,7 +53,7 @@ See the [compile.md](doc/guides/compile.md) file for the detail.
 
 ## Building documentation
 
-There are two sets of documentation in mruby: the mruby API (generated by yard) and C API (Doxygen and Graphviz)
+There are two sets of documentation in mruby: the mruby API (generated by YARD) and C API (Doxygen and Graphviz)
 
 To build both of them, simply go
 
diff --git a/tasks/doc.rake b/tasks/doc.rake
index 50dc36180..11c0bd251 100644
--- a/tasks/doc.rake
+++ b/tasks/doc.rake
@@ -9,7 +9,7 @@ namespace :doc do
     begin
       sh "mrbdoc"
     rescue
-      puts "ERROR: To generate yard documentation, you should install yard-mruby gem."
+      puts "ERROR: To generate YARD documentation, you should install yard-mruby gem."
       puts "  $ gem install yard-mruby yard-coderay"
       puts "https://yardoc.org/"
       puts "https://rubygems.org/gems/yard-mruby"